Winter Storm Watch In Gorge & Flood Watch

December 15, 2015

9:30pm Tuesday…

A major ice storm is likely on the way for the Columbia River Gorge late Wednesday night and Thursday.  A dumping of snow is also likely in parts of the Gorge too.  This event could easily rival what we saw 2 weeks ago; mainly because we have so much precipitation on the way.  As a result, the NWS has issued a Winter Storm Watch for the Gorge.  Remember a watch means an event is possible, but not imminent.

The short break with quiet weather has been nice.  But it’s pretty clear our wild December weather is going to resume soon and continue through Christmas Week.  This month is beginning to remind me of those wild winters around 1995-1997.  Specifically it seems like December 1996 right now.

This is what I’m thinking for the Gorge on Thursday:

MarkFreezingRain_Gorge

This is a somewhat unusual situation where the cold air is not already in place, but will be sucked into the Gorge tomorrow night by an approaching front and low pressure.  Cold and dry air will be sliding south through Eastern Washington.  There is still a (getting smaller) chance that models are overdoing the amount of cold air headed south.  We should have a good handle on that by sunset tomorrow.  If it’s still in the mid 40s at Yakima and Pasco tomorrow afternoon? That sure won’t inspire confidence in a real cold Gorge.

What will be typical is the distribution of frozen precipitation with a deep cold layer producing mainly snow from Cascade Locks eastward and a much thinner layer producing only freezing rain (glaze ice) in the Corbett/Cape Horn areas in the western Gorge in the east wind zone.  In between from Bridal Veil to Bonneville we’ll see a mix.  It’s even possible that at freeway level temperatures won’t be cold enough to cause issues until you get closer to Bonneville.  Regardless, I think there will be lots of schools closing Thursday from Corbett to The Dalles.  I think it’s unlikely we see freezing rain creep into the east side of the metro area like two weeks ago.  Airmass coming in isn’t that cold.  Or at least that’s the plan for now.

Whatever falls, there’s going to be A LOT of it.  Take a look at the 24 precip total from 4pm Wednesday to 4pm Thursday…about 2″ liquid is likely.

or_pcp24.48.0000

That’s a crippling ice storm, or several inches of heavy sleet, or 15″ of snow ending with sleet/ice depending on the location as mentioned above.  Our RPM shows some huge ice accumulation in spots.

RPM_ICEACCUM_USA

DON’T READ IT TOO LITERALLY (FOR A SPECIFIC SPOT); the terrain on the model doesn’t allow it to see the Gorge well.  Just note the general picture shows there is going to be a lot of ice where the cold air is thinner (near Cascade crest and western Gorge)

I’ll post again tomorrow once we’re within 24 hours of the event.

Now let’s talk flooding.  We have a bunch of rain on the way Thursday and the NWS has issued a Flood Watch once again.  As of now they are thinking some rivers will see minor flooding once again; specifically the Tualatin, Pudding, Luckiamute, Nehalem, and Johnson Creek.

MarkWarnings_FloodWatch

This is another very wet system.  Although the totals don’t look too extreme compared to earlier in the month, it’ll only add to the waterlogged slopes/soils in our area.  We can expect more slumping land and mudslides.  The southern part of our viewing area is going to be hit harder once again like this past weekend.  Our RPM shows quite a bit more rain in the south Valley than up in western Washington.

RPM_12KM_Precip_NWOR

There will be plenty more “cold rain” beyond Friday morning through next week.  Most of the next 10 days we’ll see snow above 3-4.000′.  The Thursday storm is the only one with very high snow levels.  That’s great news for Christmas Break at the ski areas!

Take a look at the next 10 day’s worth of precipitation from the latest GFS model and ECMWF.  Both show 4-6″ rain in the valleys and 10-20″ precipitation in the mountains!

It appears that we may totally blow away our wettest month on record easily at this pace.  13.35″ is the record back in December 1996.  Wow…

Chief Meteorologist Mark Nelsen